Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$6.95	8.784%	$7.5605	$7.56	$7.55	$7.60
Purchase #2	$160.77	7.326%	$172.548	$172.55	$172.55	$172.50
Purchase #3	$147.50	8.181%	$159.567	$159.57	$159.55	$159.60
Purchase #4	$34.56	8.761%	$37.5878	$37.59	$37.60	$37.60
Purchase #5	$33.63	13.202%	$38.0698	$38.07	$38.05	$38.10
Purchase #6	$228.85	4.729%	$239.6723	$239.67	$239.65	$239.70
Purchase #7	$149.59	13.275%	$169.4481	$169.45	$169.45	$169.40
7 purchase totals =	$761.85		$824.4535	$824.46	$824.40	$824.50